The present invention relates to a push button switch assembly for use in electrical circuitry.
Known push button switch assemblies are disclosed in U.S. Pat. Nos. 3,315,535; 4,496,813; 4,520,334; 5,296,826; and 5,294,900. Push button switch assemblies of the type disclosed in these patents have previously utilized a rubber seal in a groove on the outside of the push button. The seal engages inner side walls of a switch housing. The seal has been lubricated with silicone grease.
The seal prevents dust and moisture from entering a joint between the push button and housing. The seal also acts as an energy damper to prevent overtravel or pop-out of the push button when the switch is released after having been manually actuated. Overtravel of the push button tends to result when the push button is abruptly released and is rapidly accelerated towards its extended position by springs in the switch assembly.
After switch assemblies having this known construction have been used for a few years, the silicone grease tends to disappear. When the silicone grease disappears, the switch assembly tends to become nonfunctional. Nonfunctioning of the switch assembly may be caused by overtravel of the push button and/or jamming of the seal in a joint between the push button and the housing and/or other causes after the silicone grease associated with the seal disappears.